Acoustic measurement for 12% scaled model of NREL Phase VI wind turbine by using beamforming

Wind tunnel test for the 12% scaled model of NREL Phase VI wind turbine was conducted at Korea Aerospace Research Institute (KARI) low speed wind tunnel. Test condition for the scaled model was decided to match the blade tip mach number with real scale model test which was conducted at NASA Ames (80′ × 120′) Tunnel. Aerodynamic performance represented by torque of the blades was measured by using the torque sensor installed in rotating shaft and compared with real scale model test results. Acoustic noise for scaled model was also measured at closed type test section with acoustic array of 144 microphones. Time based beamforming method to identify the rotating noise source position was applied to analyze the test results. 1/3 octave band was used in post processing for various wind speeds. Test results shows that the main acoustic noise source position moves toward the blade tip as frequency increases and the noise level at low frequency below 2 kHz has much higher when the blade is in stall condition.